diff --git a/flang/lib/Lower/ConvertExpr.cpp b/flang/lib/Lower/ConvertExpr.cpp
--- a/flang/lib/Lower/ConvertExpr.cpp
+++ b/flang/lib/Lower/ConvertExpr.cpp
@@ -2693,32 +2693,36 @@
 
             if (box.getType().isa<fir::BoxType>() &&
                 fir::isPolymorphicType(argTy)) {
+              mlir::Type actualTy = argTy;
+              if (Fortran::lower::isParentComponent(*expr))
+                actualTy = fir::BoxType::get(converter.genType(*expr));
               // Rebox can only be performed on a present argument.
               if (arg.isOptional()) {
                 mlir::Value isPresent =
                     genActualIsPresentTest(builder, loc, box);
                 box = builder
-                          .genIfOp(loc, {argTy}, isPresent,
+                          .genIfOp(loc, {actualTy}, isPresent,
                                    /*withElseRegion=*/true)
                           .genThen([&]() {
-                            auto rebox = builder
-                                             .create<fir::ReboxOp>(
-                                                 loc, argTy, box, mlir::Value{},
-                                                 /*slice=*/mlir::Value{})
-                                             .getResult();
+                            auto rebox =
+                                builder
+                                    .create<fir::ReboxOp>(
+                                        loc, actualTy, box, mlir::Value{},
+                                        /*slice=*/mlir::Value{})
+                                    .getResult();
                             builder.create<fir::ResultOp>(loc, rebox);
                           })
                           .genElse([&]() {
                             auto absent =
-                                builder.create<fir::AbsentOp>(loc, argTy)
+                                builder.create<fir::AbsentOp>(loc, actualTy)
                                     .getResult();
                             builder.create<fir::ResultOp>(loc, absent);
                           })
                           .getResults()[0];
               } else {
-                box =
-                    builder.create<fir::ReboxOp>(loc, argTy, box, mlir::Value{},
-                                                 /*slice=*/mlir::Value{});
+                box = builder.create<fir::ReboxOp>(loc, actualTy, box,
+                                                   mlir::Value{},
+                                                   /*slice=*/mlir::Value{});
               }
             } else if (Fortran::lower::isParentComponent(*expr)) {
               fir::ExtendedValue newExv =
diff --git a/flang/test/Lower/polymorphic.f90 b/flang/test/Lower/polymorphic.f90
--- a/flang/test/Lower/polymorphic.f90
+++ b/flang/test/Lower/polymorphic.f90
@@ -1067,6 +1067,25 @@
 ! CHECK: %[[CONV:.*]] = fir.convert %[[REBOX]] : (!fir.box<!fir.type<_QMpolymorphic_testTp1{a:i32,b:i32}>>) -> !fir.class<!fir.type<_QMpolymorphic_testTp1{a:i32,b:i32}>>
 ! CHECK: fir.call @_QMpolymorphic_testPprint(%[[CONV]]) {{.*}} : (!fir.class<!fir.type<_QMpolymorphic_testTp1{a:i32,b:i32}>>) -> ()
 
+  subroutine takes_p1_opt(a)
+    class(p1), optional :: a
+  end subroutine
+
+  subroutine test_parent_comp_opt(p)
+    type(p2), allocatable :: p
+    allocate(p)
+    call takes_p1_opt(p%p1)
+  end subroutine
+
+! CHECK-LABEL: func.func @_QMpolymorphic_testPtest_parent_comp_opt(
+! CHECK-SAME: %[[ARG0:.*]]: !fir.ref<!fir.box<!fir.heap<!fir.type<_QMpolymorphic_testTp2{a:i32,b:i32,c:f32}>>>> {fir.bindc_name = "p"}) {
+! CHECK: %[[LOAD_ARG0:.*]] = fir.load %[[ARG0]] : !fir.ref<!fir.box<!fir.heap<!fir.type<_QMpolymorphic_testTp2{a:i32,b:i32,c:f32}>>>>
+! CHECK: %[[RES:.*]] = fir.if %{{.*}} -> (!fir.box<!fir.type<_QMpolymorphic_testTp1{a:i32,b:i32}>>) {
+! CHECK:   %[[REBOX:.*]] = fir.rebox %[[LOAD_ARG0:.*]] : (!fir.box<!fir.heap<!fir.type<_QMpolymorphic_testTp2{a:i32,b:i32,c:f32}>>>) -> !fir.box<!fir.type<_QMpolymorphic_testTp1{a:i32,b:i32}>>
+! CHECK:   fir.result %[[REBOX]] : !fir.box<!fir.type<_QMpolymorphic_testTp1{a:i32,b:i32}>>
+! CHECK: %[[CONV:.*]] = fir.convert %[[RES]] : (!fir.box<!fir.type<_QMpolymorphic_testTp1{a:i32,b:i32}>>) -> !fir.class<!fir.type<_QMpolymorphic_testTp1{a:i32,b:i32}>>
+! CHECK: fir.call @_QMpolymorphic_testPtakes_p1_opt(%[[CONV]]) {{.*}} : (!fir.class<!fir.type<_QMpolymorphic_testTp1{a:i32,b:i32}>>) -> ()
+
 end module
 
 program test